Field of the Invention
This invention relates, in general, to braking devices and, in particular, to a new and useful fluid pressure operated braking device having a linkage setter and, in particular is useful for rail vehicles.
The invention relates to a brake actuation unit with a hydraulic or pneumatic cylinder, in particular for rail vehicles, having an installed single-action linkage setter for maintaining a clearance between the brake surfaces. A linkage setter, containing two telescopic parts, of which one part is formed as a threaded spindle and the other as a tubular part, is firmly connected with a nut which is screwed on the spindle with a non-selflocking thread. The tubular part carrying the nut has coupling surfaces which cooperate with coupling surfaces on the piston. A tensioned actuating spring is disposed between the piston and an output head.
Such a device is known, for example, from German Pat. No. 2,201,082 which, however, has the disadvantage that the resetting of the device after complete compensation of play for the installation of new, as yet unworn brake linings is expensive and complicated. Another disadvantage of this known device is that even when the actual clearance between the abutting friction surfaces (of the brake shoe as well as the brake surface on the brake disks) is smaller than the desired clearance, readjustment occurs until the desired clearance exists. This is especially disadvantageous if ice has formed on the friction surfaces, because then the clearance is increased beyond the acceptable amount. The device according to German Pat. No. 2,830,361 is based on a similar principle for adjustment in the case of worn brake linings, but in this case also complicated measures are necessary in order to bring the device to the initial position again for new brake linings, from which readjustment is then possible again if the wear of the brake lining results in too great a clearance.